As its name implies, the dye transfer process literally involves transferring dyes
(cyan, magenta, and yellow) in succession and in careful registration onto a sheet of
gelatin-coated paper. Porter remained committed to the dye transfer process, both before
and after the invention of simpler and more commonly used color papers, because it
delivered richly colored prints and allowed him to control the exact hues and contrast
of each final print.

Porter would initially shoot a scene generally on 4-by-5-inch inch transparency film,
recording the exposure conditions on a card.

After developing the transparency, he would create three separation negatives
by exposing the transparency three times onto three separate sheets of 4-by-5-inch
black-and-white film. He would make the first exposure through a red filter, the
second exposure through a green filter, and the third through a blue one.

He then would create three matrices by shining white light through each separation
negative via enlargement onto its own sheet of matrix film. (Each matrix would hold
an image the same size as the final print.) The resulting matrices are positive
images that have a slight relief. The thicker parts print as darker areas.
Generally he would sandwich the separation negatives with masks to further control
contrast. These masks were softly focused versions of the darker information on the
separation negatives.

To make a print, Porter would soak the red-filtered matrix in a bath of cyan dye,
the green-filtered matrix in magenta dye, and the blue-filter matrix in yellow dye.
Each matrix would soak up the dye according to its thickness, with the thicker areas
picking up more color. He then would place one end of each dye-carrying matrix, in turn,
onto register pins at the end of a special gelatin-coated paper and carefully roll it
in contact with the paper. After about four minutes, when the dye had completely
transferred to the paper, he would lift the matrix off, wash it, and register and roll
the next matrix into place. The three dyes together would produce a full color print.

He could subtly change the hues and contrast of each print by changing the acidity of
his dye baths and by resoaking and rerolling one or more of the matrices onto the
receiving paper. He would record the various "recipes" used to achieve a good print
in an ongoing printing notebook.

Once settling on a printing "recipe," Porter would write that recipe on a printing
card for future reference, in case he had to make another print of that same image
in the future.